Geosystems and Geoenvironment最新文献

{"title":"Geospatial assessment of soil erosion in the Basantar and Devak watersheds of the NW Himalaya: A study utilizing USLE and RUSLE models","authors":"Ajay Kumar Taloor ,&nbsp;Varun Khajuria ,&nbsp;Gurnam Parsad ,&nbsp;Shikha Bandral ,&nbsp;Sugandha Mahajan ,&nbsp;Sachchidanand Singh ,&nbsp;Meenakshi Sharma ,&nbsp;Girish Ch Kothyari","doi":"10.1016/j.geogeo.2025.100355","DOIUrl":"10.1016/j.geogeo.2025.100355","url":null,"abstract":"<div><div>Soil erosion poses a substantial threat to environmental and human sustainability, intensified by anthropogenic interference, climate fluctuations, and socio-economic modifications. This study presents a meticulous and systematic analysis of soil erosion within the Basantar and Devak watersheds of the north-western Himalaya, employing geospatial technologies integrated with the USLE (Universal Soil Loss Equation) and RUSLE (Revised Universal Soil Loss Equation) modeling techniques. To derive the USLE and RUSLE based soil loss, various equation-based parameters such as rainfall (R), length slope factor (LS), cover management (C), conservation practice factor (P), and slope erodibility factor (K) were derived to assess the spatial soil loss in the study area. Based on both model outputs spatial maps have been derived in the Geographic Information System (GIS) platform to determine the soil loss in the study area. The results have been classified into five categories: very high, high, medium, low, and very low areas of soil erosion. Further, the analytical approach also involved the derivation of various satellite data-based soil indices to juxtapose remotely sensed soil loss results, enabling a more detailed understanding of soil loss dynamics in the watersheds. The comprehensive analysis demonstrated the practicality of the employed models in formulating geospatial soil erosion databases, aiding future research, planning, conservation strategies, and climate impact assessment, therefore, laying a foundation for informed environmental decision-making and sustainable land-use practices. The multifaceted exploration of soil erosion in the Basantar and Devak watersheds through intricate modeling and geospatial technologies accentuates the study's significance in advancing soil conservation research, and the potential applications of these models in varied environmental contexts.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"4 2","pages":"Article 100355"},"PeriodicalIF":0.0,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting urban landslides in the hilly regions of Bangladesh leveraging a hybrid machine learning model and CMIP6 climate projections","authors":"Md․ Ashraful Islam ,&nbsp;Musabbir Ahmed Arrafi ,&nbsp;Mehedi Hasan Peas ,&nbsp;Tanvir Hossain ,&nbsp;Md Mehedi Hasan ,&nbsp;Sanzida Murshed ,&nbsp;Monira Jahan Tania","doi":"10.1016/j.geogeo.2025.100354","DOIUrl":"10.1016/j.geogeo.2025.100354","url":null,"abstract":"<div><div>Landslides pose significant risks to infrastructure and human lives in cities, exacerbated by climate change. Therefore, a reliable predictive landslide model is crucial for mitigation, especially in resource-limited nations. This study employs hybrid machine learning (ML) techniques and climate projections to predict landslides in the Chattogram development area (CDA) of Bangladesh – a rapidly growing urban city in Bangladesh. The model was trained using diverse geospatial parameters including topographical, hydrological, soil, and geological parameters, along with an updated landslide inventory, enabling spatially explicit predictions of landslide susceptibility. To incorporate future climate scenarios, we utilized the Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Model (GCM), projecting climate impacts under SSP1-2.6 and SSP5-8.5 scenarios for the periods of 2021–2040, 2041–2060, 2061–2080, and 2081–2100, respectively. These scenarios reflect different pathways of greenhouse gas emissions, providing a range of possible future climate conditions. We tested six ML classifiers: random forest (RF), extra trees (ExT), support vector machine (SVM), logistic regression (LR), Bernoulli Naïve Bayes (bNB), and K-nearest neighbor (KNN). Each base model demonstrated high accuracy (&gt;90 %) but combining them improved both accuracy and computational efficiency. The LR-bNB hybrid model outperformed all others, effectively mapping landslide susceptibility in the study area for the current timeframe and future projections. Our results revealed significant variability in landslide-prone areas across the area, with 12 % of the region categorized as high to very high risk, a figure that slightly rises with predicted increased rainfall due to climate change. The present study demonstrates the efficacy of a hybrid ML model for nowcasting as well as forecasting landslide susceptibility under future climate scenarios. These findings offer valuable insights for proactive risk management and infrastructure planning in the CDA, helping to safeguard communities and improve resilience against future landslide events.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"4 2","pages":"Article 100354"},"PeriodicalIF":0.0,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143643233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Composition of olivines and spinel group minerals in aillikites from the Bushkanay dyke, South Siberian Craton: Insights into alkaline melt sources and evolution","authors":"Yazgul Nugumanova ,&nbsp;Anna Doroshkevich ,&nbsp;Anastasia Starikova ,&nbsp;Jonathan Garcia","doi":"10.1016/j.geogeo.2023.100247","DOIUrl":"10.1016/j.geogeo.2023.100247","url":null,"abstract":"<div><div>The potential sources and conditions that control the formation and evolution of alkaline melts are far from being fully understood. To address some of these fundamental questions, we have focused on the composition of olivines and spinel group minerals in aillikites from the Bushkanay dyke in the Siberian Craton. These ultramafic carbonate-rich lamprophyres contain 40–50 vol% fresh olivine macrocrysts (200–600 µm) within a groundmass consisting of phlogopite (60%), magnetite (15%), perovskite (10%), apatite (5%), calcite (3%), chromite (1%), clinopyroxene (up to 1%), barite (up to 1%), serpentine and chlorite (up to 4%). Two types of compositional zoning in olivine have been recognized: (1) Mg-rich cores consisting of a relatively high #Mg (86-89) and NiO (0.25–0.4 wt%); (2) Fe-rich cores with a relatively low #Mg (82-86) and NiO (0.10–0.25 wt%). Both types of olivine cores are igneous and crystallize from an ultramafic carbonate-rich melt. The Mg#-poor (Fe-rich) cores were derived from an early and more evolved aillikitic melt and were later entrained by a more primitive melt, responsible for the formation of the Mg#-rich (Mg-rich) cores. The spinels exhibit a more complex zoning with four major growth zones: (1) an aluminum chromite core; (2) an Fe-chromite and Cr-magnetite transitional zone; and (3) a Ti-magnetite rim. The most primitive spinels of Al-chromite compositions crystallized directly from undifferentiated pulse of the melt, while further growth involved a gradual decrease in Cr due to the crystallization of Cr-rich spinels, while Al remained the same due to the absence of early phlogopite. Our results on olivines and spinels suggest that the aillikites of the Bushkanay dyke were derived from a phlogopite-bearing carbonatized peridotite source. This idea is also supported by the presence of phlogopite, calcite, and amphibole as major phases in the chromite melt inclusions.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100247"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138991160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical evolution of major and minor minerals in rocks of the Arbarastakh complex (Aldan shield, Republic of Sakha, Yakutia)","authors":"Mikhail Nikolaevich Kruk ,&nbsp;Anna Gennadievna Doroshkevich ,&nbsp;Ilya Romanovich Prokopyev ,&nbsp;Ivan Aleksandrovich Izbrodin","doi":"10.1016/j.geogeo.2024.100271","DOIUrl":"10.1016/j.geogeo.2024.100271","url":null,"abstract":"<div><div>The alkaline-ultrabasic carbonatite complex Arbarastakh is located in the southwestern part of the Siberian Craton. In addition to ultrabasic rocks such as pyroxenites and ijolites, various types of carbonatite dikes, phoscorites, and aillikites are present in the massif. Based on their modal and compositional characteristics, as well as the chemical composition of minerals, the rocks of the Arbarastakh complex have been divided into three groups: \"aillikite\", \"phoscorite\", and \"alkaline-silicate and carbonatite\" groups. The chemical compositions of olivines, phlogopites and spinellides indicate that aillikites are the least differentiated rocks in the complex. The compositional differences of micas from the \"phoscorite\" and \"alkaline-silicate and carbonatite\" groups support the liquation of the aillikite melt into two immiscible silicates and CPIO (carbonate-phosphate/iron-oxide-rich) melts. After liquation, for the \"phoscorite\" and \"alkaline-silicate and carbonatite\" groups, evolution follows fractional crystallization. Pyroxene-phlogopite-calcite and calcite carbonatites probably resulted from metasomatic alteration of silicate phases by apatite-dolomite carbonatites, which is confirmed by structural-textural features and the overlapping compositions of phlogopites, apatites and pyroxenes from calcite carbonatites and those from pyroxenites and ijolites.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100271"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140282740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconstructions of mantle structure beneath the Anabar Shield kimberlites – Similarities and differences","authors":"Igor V. Aschepkov ,&nbsp;Sergei I. Kostrovitsky ,&nbsp;Svetlana A. Babushkina ,&nbsp;Nikolai S. Medvedev","doi":"10.1016/j.geogeo.2024.100282","DOIUrl":"10.1016/j.geogeo.2024.100282","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Comparisons of mantle xenocrysts from Lower Triassic kimberlites in the Anabar Shield (Ary-Mastakh, Dyuken, Kuranakh and Orto-Yargyn fields) have shown essential differences from the xenocrysts in the Olenek River Basin (Chomurdakh field). Xenoliths in the Anabar Shield and its northern fields are very rare; they include mainly garnet dunites and harzburgites, and less commonly, pyroxenites and eclogites.&lt;/div&gt;&lt;div&gt;PTXFO&lt;sub&gt;2&lt;/sub&gt; diagram reconstructions for the Boomerang pipe in the Ary-Mastakh field located in the suture zone of the Daldyn and Magan terranes have used monomineral thermobarometry to show that the Opx in rare lherzolitic pyropes formed between 6 and 7.5 GPa. Eclogites represent the mantle heated to the middle pyroxenite layer, and in these terranes the formation of Cr-less pyroxenites are linked to plume melt interactions with the eclogites. In the Dyuken, Kuranakh and Orto-Yargyn fields, the garnet advective trend starts from 7.5 GPa, while the asthenosphere – lithosphere boundary is found at 6 GPa, suggesting that the middle pyroxenite layer was heated and metasomatized. The lower and particularly mid-mantle parts of these fields also contain abundant eclogites. In the Chomur field, lherzolitic and pyroxenitic pyropes form from 7 GPa, while the captured materials mainly represent the upper mantle (4 GPa). All pipes show a similar mantle layering, consisting of seven parts and determined by the clustering of PT estimates for garnets, Cr-spinels, and pyroxenes. In the Boomerang pipe, the Cr-clinopyroxenes and pyropes show REE spectra with varying fan-shaped slopes, (La/Yb)n of 10–100 for pyropes, and HREE for garnets. Spider diagrams reveal peaks for Th, and troughs for U, Nb, Ta, and Pb. Eclogitic garnets and omphacites show minimum values of Eu and Nb, Ta, Zr, and Hf. REEs in ilmenites show a joint increase in LREE and HFSE for Mg to Fe-rich varieties with the degree of differentiation. Most depleted pyropes from Kuranakh have V-U shaped REE patterns, Ba and U peaks. The HFSE minima represents dunites from the arc and back-arc mantle, and the fertilization produces an increase in incompatible elements and sometimes large ion lithophile element (LILE) levels for lherzolitic pyropes. The pyroxenitic garnets display happed REE and the Cpx shows varying LILE and HFSE correlating with the (La/Yb)&lt;sub&gt;n&lt;/sub&gt;.&lt;/div&gt;&lt;div&gt;The Chomur pipe contains predominantly harzburgite-lherzolite garnets with minima Ba and Sr, in addition to various incompatible elements. Cpx shows similar variations with mainly depleted HFSE patterns. The marginal parts of the subcratonic lithospheric mantle (SCLM) of the Anabar Shield are extremely enriched in eclogitic deep-seated material. This is especially seen in the lower SCLM parts, demonstrating thermobarometric trends and features similar to the diamond inclusions from the Ebelyakh (Mayat) placers. The mantle column beneath several pipes (Los’, Universitetskaya, Kuranakh) contain Cr amphiboles","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100282"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Olivine composition of calcite-carbonatite from Sevvattur carbonatite alkaline complex, Dharmapuri Rift Zone, Southern Granulite Terrain, India","authors":"Tushar Meshram ,&nbsp;Kirtikumar Randive","doi":"10.1016/j.geogeo.2023.100235","DOIUrl":"10.1016/j.geogeo.2023.100235","url":null,"abstract":"<div><div>Olivine in carbonatites worldwide is mainly of Mg-rich composition (forsterite: Fo₈₅ and Fo₉₉). However, the occurrence of fayalite (Fo_&lt;50) is extremely rare except few localities. The Sevvattur carbonatite alkaline complex (SCAC) is part of large Tirrupattur carbonatite-alkaline complex (TCAC), Southern India, which consists of early to late differentiated/fractionated products from dunite-wehrlite-shonkinite-carbonatite to ferrosyenite. In TCAC olivine composition shows decreasing Fo₉₃ to Fo₀₆ contents from early dunite to more evolved ferrosyenite. We report here an occurrence of low-Ni, olivine with intermediate Fo_60-65 content and low 100*Mn/Fe, Ni/Co, V/Sc ratios from the SCAC. Textural and compositional evidence reveals the xenocrystic (exotic) nature of olivine and possibly linked with multiple stages of crystal melt interaction in the protracted magmatic evolution and associated metasomatic processes during the interaction of peridotite lithosphere with carbonatite magma in the TCAC at low temperature and shallow depth. It is concluded that the olivine in the Sevvattur Carbonatite Olivine provide the missing link or compositional gap during the evolution of the TCAC of early to late differentiated products from dunite (Fo_90-91)-wehrlite (Fo_70-72)-shonkinite (Fo_72-77)-carbonatite (Fo_∼90 _{and 63–65} present study) to ferrosyenite (Fo_03-06).</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100235"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134918273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative mineralogy, geochemistry and petrology of the Beloziminsky Massif and its aillikite intrusions","authors":"Igor V. Ashchepkov ,&nbsp;Sergei M. Zhmodik ,&nbsp;Dmitry M. Belyanin ,&nbsp;Olga N. Kiseleva ,&nbsp;Nikolai S. Karmanov ,&nbsp;Nikolai S. Medvedev","doi":"10.1016/j.geogeo.2024.100309","DOIUrl":"10.1016/j.geogeo.2024.100309","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Beloziminsky Massif (BZM) is an alkaline ultramafic carbonatite complex that includes carbonatites, ijolites, meltegites, and syenites (abbreviated as the CIMS suite) as well as aillikite intrusions that range in age from 645–621 Ma. Aillikite intrusions also occur in the Yuzhnaya Pipe (YuP), located about 16 km eastward of the BZM. Over 5400 analyses in total were conducted to compare mineralogy and geochemistry of different rock types in this study; of these, 24 CIMS samples (&gt;1100 analyses) and about 16 aillikites (&gt;2300 analyses) were collected from within the BZM; the rest are aillikite mineral samples from pipes and dykes outside the massif (&gt;2000 analyses). The results suggest significant differences in sources for rock-forming minerals, less so for the accessories. The pyroxenes in aillikite correspond either to mantle Cr-diopside xenocrysts or megacrystic augites. Low-Na Ti-augites and diopsides as well as aegirines are prevalent in the CIMS intrusive suite. Amphiboles show a considerably long compositional trend, from hornblendes to richterites. Dolomitic carbonatites include admixtures of Na, K, and Ba while calcium carbonatites often contain Sr. The carbonate-rich aillikitics are enriched either in Mg or Ca. The CIMS rocks, particularly the Ca-Mg carbonatites, often include siderites. Thermobarometry for the YuP samples, collected from outside the BZM and containing Cr-diopsides, Cr-phlogopites and Cr-spinels, suggest a formation pressure of 2–4 GPa and a temperature of 800–1250°C; augite xenocrysts with elevated HFSE, U, Th, and Al-augites trace a 90 mW/m&lt;sup&gt;2&lt;/sup&gt; geotherm.&lt;/div&gt;&lt;div&gt;The huge thermal impact of the plume that triggered the break-up of Rodinia also created a series of ultramafic–alkaline–carbonatite massifs. Initially, the aillikites in the mantle were likely produced by the plume-induced melting of carbonated metasomatites containing ilmenite, perovskites, apatites, amphiboles and phlogopites which, in turn, were created by subduction-related melts. Any additional enrichment in the ore components might have occurred subsequentlty in the lower crust, due to liquation. The aillikites inside the BZM contain low-temperature clinopyroxenes tracing a steep advective geotherm (0.4–1.5 GPa); they also contain clots, related to intermediate depth magma chambers, together with CIMS pyroxenes and amphiboles. This suggests that the liquation of aillikites was accompanied by density separation and assimilation and fractional crystallization (AFC) fractionation with the participation of crustal material. Trace elements (especially REEs) in silicate minerals, carbonates, apatites, and accessories (perovskites, pyrochlores, monazites, columbites, zircons, ancylites, etc.) show a general rise in REE levels and La/Yb&lt;sub&gt;n&lt;/sub&gt; ratios from aillikites to ijolites, and later to Fe- carbonatites. The presence of zircons, monazites, columbite-tantalites, and other Zr-Hf and Ta-Nb minerals like perovskites and tan","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100309"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142704316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated hydrological modeling and water resource assessment in the Mayurakshi River Basin: A comprehensive study from historical data to future predictions","authors":"Swetasree Nag ,&nbsp;Malabika Biswas Roy ,&nbsp;Pankaj Kumar Roy","doi":"10.1016/j.geogeo.2024.100308","DOIUrl":"10.1016/j.geogeo.2024.100308","url":null,"abstract":"<div><div>This study employs the SWAT hydrologic model to integrate climatological and hydrological processes for an in-depth analysis of the Mayurakshi River Basin. Utilizing the Markov chain model, the study evaluates water availability, flow patterns, and the basin's response to various climatic and land-use scenarios. Over 30 years of daily observed river discharge data were rigorously calibrated, validated, and analyzed for uncertainty, with critical data from the Massanjore Dam and Tilpara Barrage gauge stations characterizing the river's hydrological behavior. The result suggests the watershed received an average annual precipitation of 1432.4 mm, with evapotranspiration accounting for 40% of total water loss (578.4 mm). Surface runoff constituted over 90% of the total discharge, highlighting its importance for agricultural practices, particularly during the dry season. However future projections (2021–2031) indicate a significant decrease in mean annual precipitation (1404.7 mm) and a drop in evapotranspiration (542.1 mm or 38% of mean precipitation), attributed to reduced vegetation cover and increased settlement, leading to enhanced surface runoff. By quantifying internal renewable blue water, evapotranspiration, and soil water, this research provides crucial data for long-term water resource planning and assessment. The findings are valuable for national, regional, and transboundary water management agencies, offering insights into sustainable water resource management under changing climatic and different land-use conditions.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100308"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141843241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrology of ijolite xenoliths entrained in a nephelinite dyke from the Kamthai area, Late Cretaceous polychronous Sarnu-Dandali alkaline complex, North-West India: Evidence for recurrent magmatic pulses and magma mixing","authors":"Sudipa Bhunia ,&nbsp;N.V. Chalapathi Rao ,&nbsp;Debojit Talukdar ,&nbsp;Rohit Pandey ,&nbsp;Bernd Lehmann","doi":"10.1016/j.geogeo.2023.100248","DOIUrl":"10.1016/j.geogeo.2023.100248","url":null,"abstract":"<div><div>The Late Cretaceous (89–65 Ma) Sarnu-Dandali alkaline complex is intrusive into the Neoproterozoic (∼750 Ma) Malani Igneous Suite of rocks in North-Western India. This complex represents a polychronous setup owing to the available age groups of varied rock types involving nephelinites, alkali pyroxenites, syenites, phonolites, ijolites, carbonatites and lamprophyres. In this study, we report xenoliths of ijolite up to 2 mm in size, comprising minerals such as aegirine, nepheline, sodalite, apatite, sphene, fluorite, Ti-rich andradite, and perovskite entrained in the host nephelinite from this complex. Pyroxene thermobarometry for both host and xenoliths reveals that the xenoliths crystallized around 876–1114°C; 4.6–18 kbar (<em>Kd_cpx</em>_−melt ∼0.164), whereas the host magma crystallized around 800–1165°C and 4.5–17.9 kbar (<em>Kd_cpx</em>_−melt ∼0.44). The redox conditions of the magma are also estimated from Fe-Nb oxy barometry of perovskite and the log oxygen fugacity varies from -2.5 to -3.7 (ΔNNO), showing a resemblance with that of the world-wide kimberlites derived from the cratonic mantle. Furthermore, the composition as well as the barometric study of clinopyroxenes from both the host and the xenoliths, suggest multiple shallower magma chambers composed of ijolite and nephelinite magmas which were activated by different magmatic pulses, thereby forming a complex magmatic plumbing system.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100248"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139023265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal state and nature of the lower crust in the Baikal Rift Zone: Insight from xenoliths of Cenozoic and Paleozoic magmatic rocks","authors":"I.V. Ashchepkov ,&nbsp;A.A. Tsygankov ,&nbsp;G.N. Burmakina ,&nbsp;N.S. Karmanov ,&nbsp;S.V. Rasskazov ,&nbsp;I.S. Chuvashova ,&nbsp;Y. Ailow","doi":"10.1016/j.geogeo.2024.100305","DOIUrl":"10.1016/j.geogeo.2024.100305","url":null,"abstract":"<div><div>Preliminary studied lower crust and Moho of Baikal Rift (BR) was investigated using pyroxenite xenoliths and xenocrysts from Cenozoic volcanoes to determine the structure, thermal conditions and composition of the transitional zone from the crust to mantle and influence of plumes on it. Samples from Vitim Plateau (Miocene picrite basalts) SW part of BR, Dzhida River Basin (Bartoy volcanoes) located at SE of BR and Tunka axial Valley (Karierny volcanoes) to the West from Baikal were studied for major components using electron microprobe and electron microscope and for trace elements with the inductively connected mass-spectrometry with laser ablation. For the comparison, the lower crust xenocrysts from the Angara Vitim batholite were also included in this study. The PT estimates for minerals are mostly refer to the Moho boundary or are locating just beneath it giving the vast range of temperatures. Beneath the Moho, they trace 90 mw/m² geotherm. Within the crust, temperature regime varies from the conductive to advective. Pyroxene xenocrysts and pyroxenite xenoliths mainly trace 90 mw/m² SEA plume geotherm. The levels of the melt intrusions are overheated to 1350°C. The granulites are typically represent the colder conditions than SEA geotherm. Xenocrysts from Angara Vitim batholith magmas reveal more depleted material of lower crust than those found in Cenozoic lavas and possibly are skialites. The xenocrysts and granulite xenoliths in Cenozoic lavas are mainly basic cumulates. The rocks of the lower crust became more acid to the upper part.</div><div>The lateral variations in the lower crust sampled material show enrichment in K₂O at the boundary with the Siberian Craton in Tunka, more metasomatic and hydrous nature in Dzhida zone and more basic and CaO rich characteristic in Vitim area. These data give the evidence for the conditions of origin of the magmas of Angara-Vitim Batholith (AVP) (275–310 Ma), which was created due to interaction of hot spot with the crust in Baikal and Transbaikalia. Initially this hot generated kimberlites and basalts in northern (420–390 Ma) and central part of Yakutia (370–440 Ma) in time, migrated to – and eeastern Sayan Mountain formed Ingashi lamproites -kimberlites (310 Ma), than plume was spreading to south beneath the crust in Transbaikalia and created AVP. After it returned to central and northern Siberia, it generated Permo-Triassic Siberian trap province.</div></div>","PeriodicalId":100582,"journal":{"name":"Geosystems and Geoenvironment","volume":"3 4","pages":"Article 100305"},"PeriodicalIF":0.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141713730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}